See this forum posting for a potential fix, if your using an ATI graphics card:

http://forum.lazy8studios.com/index.php?PHPSESSID=h1d37r13a2d2ccnk5c5j6b2c94&topic=475.msg837#msg837

This is a fix for the bug where Cogs launches with the following output:

Shader compile log for data/effects/TextureBumpCubemap.fsh:
Fragment shader failed to compile with the following errors:
ERROR: 0:41: error(#132) Syntax error: ‘smooth’ parse error
ERROR: error(#273) 1 compilation errors.  No code generated

Apparently the word “smooth” is reserved, but only on ATI cards in Linux.  The fix is to modify the following file.

~/games/cogs/data/effects/TextureBumpCubemap.fsh

Just do a global replace of the word “smooth” with “Smooth”.

A huge thanks to Renee Marie Jones, who figured this one out

I wasn’t seeing that particular output on the console, and the screen was just blank/black and I could hear the music. But, this fix did work for me on Ubuntu Linux 10.10 (Maverick).